Sunflower is one of the few crop species that originated in North America. It was probably domesticated by Native American tribes around 1000 B.C. The first Europeans observed sunflower cultivated in many places across North America, from southern Canada to Mexico. Sunflower was probably first introduced to Europe through Spain, eventually reaching Russia where it was extensively cultivated. Selection for high oil began in Russia in 1860 and resulted in oil content increasing from 28 percent to 50 percent. These high-oil lines from Russia were introduced into the United States after World War II. The later discovery of the male-sterile and restorer gene system made hybrids feasible and increased commercial interest in the crop. Production of sunflowers subsequently rose dramatically in the Great Plains states as marketers found new niches for the seeds as an oil crop, a birdseed crop, and as a human snack food.
The cultivated sunflower (Helianthus annuus L.) is a major worldwide source of vegetable oil. In the United States, the major sunflower producing states are the Dakotas, Minnesota, Kansas, Colorado, Nebraska, Texas and California, although most states have some commercial acreage. Sunflower oil production in the United States was 2.26 million pounds in 2003. Non-oil production was 406,000 pounds. Non-oil sunflowers averaged 1,256 pounds per acre in 2003, while oil sunflowers had an average yield of 1,206 pounds per acre in 2003.
Sunflowers are considered oilseeds, along with cottonseed, soybeans and canola and the growth of sunflower as an oilseed crop has rivaled that of soybean. The oil accounts for 80 percent of the value of the sunflower crop, as contrasted with soybean, which derives most of its value from the meal. Sunflower oil is generally considered a premium oil because of its light color, high level of unsaturated fatty acids, lack of linolenic acid, bland flavor and high smoke points. The primary fatty acids in the oil are oleic and linoleic with the remainder consisting of palmitic and stearic saturated fatty acids.
Non-dehulled or partly dehulled sunflower meal has been substituted successfully for soybean meal in isonitrogenous (equal protein) diets for ruminant animals, as well as for swine and poultry feeding. Sunflower meal is higher in fiber, has a lower energy value and is lower in lysine but higher in methionine than soybean meal. Protein percent of sunflower meal ranges from 28 percent for non-dehulled seeds to 42 percent for completely dehulled seeds.
In addition to its use in food and food products for humans and animals, sunflower oil also has industrial uses. It has been used in paints, varnishes and plastics because of good semidrying properties without the color modification associated with oils high in linolenic acid. It has also been used in the manufacture of soaps, detergents and cosmetics. The use of sunflower oil (and other vegetable oils) as a pesticide carrier, and in the production agrichemicals, surfactants, adhesives, fabric softeners, lubricants and coatings has been explored. Considerable work has also been done to explore the potential of sunflower as an alternate fuel source in diesel engines because sunflower oil contains 93 percent of the energy of U.S. Number 2 diesel fuel (octane rating of 37). More recently, sunflower oil has been proposed as a source of hydrogen for hydrogen fuel cells (BBC News, Aug. 26, 2004).
Sunflower is an annual, erect, broadleaf plant with a strong taproot and a prolific lateral spread of surface roots. Stems are usually round early in the season, angular and woody later in the season, and normally unbranched. The sunflower head is not a single flower (as the name implies) but is made up of 1,000 to 2,000 individual flowers joined at a common receptacle. The flowers around the circumference are ligulate ray flowers without stamens or pistils; the remaining flowers are perfect flowers with stamens and pistils. Anthesis (pollen shedding) begins at the periphery and proceeds to the center of the head. Since many sunflower varieties have a degree of self-incompatibility, pollen movement between plants by insects is important, and bee colonies have generally increased yields.
The development of a cytoplasmic male-sterile and restorer system for sunflower has enabled seed companies to produce high-quality hybrid seed. Most of these have higher yields than open-pollinated varieties and are higher in percent oil. Performance of varieties tested over several environments is the best basis for selecting sunflower hybrids. The choice should consider yield, oil percent, maturity, seed size (for non-oilseed markets), and lodging and disease resistance.
As a crop, sunflower yields are reduced, but rarely eliminated, by weeds, which compete with sunflower for moisture and nutrients and occasionally for light. Sunflower is a strong competitor with weeds, especially for light, but does not cover the ground early enough to prevent weed establishment. Therefore, early season weed control is essential for good yields; successful weed control should include a combination of cultural and chemical methods. Almost all North American sunflower plantings are cultivated and/or harrowed for weed control, and over ⅔ are treated with herbicides.
The imidazolinones are a class of herbicides that control a broad spectrum of weeds at low rates and are used throughout the world in legumes, cereals, forests, and plantation crops. These herbicides are widely used, not only because of their efficacy, but also because of their low mammalian toxicity and low environmental impact. The availability of imidazolinone-resistant crops offers many benefits and advantages to the grower by allowing the development of a very flexible weed management program. Because of the broad-spectrum activity and flexible application techniques of the imidazolinones, a weed management program that utilizes a resistant crop can be based on the weeds that need to be controlled with less concern of the relative selectivity of the herbicide. Imidazolinone-resistant crops thus can be an effective weed management tool.
The features of commercially competitive plant varieties generally include more than high yield with excellent standability. While yield is the single most critical input that affects the crop producer's profit, producers expect consistency of yield from year to year, disease resistance, other value-added traits and, more recently, herbicide resistance. The addition of herbicide resistance has created both opportunities as well as tremendous challenges in production agriculture.
References: Putnam, et al. 1990, Sunflower in Alternative Field Crops Manual, University of Wisconsin-Extension, Cooperative Extension; University of Minnesota: Center for Alternative Plant & Animal Products; Minnesota Extension Service; M. Boland and J. Stroade 2004, Sunflower Industry Profile, Department of Agricultural Economics, Kansas State University; Agricultural Marketing Resource Center; Stephen Duke, Ed., 1996, Herbicide-Resistant Crops. Agricultural, Environmental, Economic, Regulatory, and Technical Aspects, CRC Press; U.S. Pat. No. 4,627,192; U.S. Pat. No. 5,276,264; and U.S. Pat. No. 6,388,113.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification.